The first picture is just a diagram of how it's wired (not my picture, stole it off google) and the bottom picture is how it looks all put together.
The only thing about the diagram, you can ignore terminals "7" and "8" because that is the cooling function of the thermostat. I just left these...
You could also try an inkbird thermostat. They are only about $15-20 on amazon and you can wire those to an outlet ($2-3 any hardware store, or amazon). Then you would just plug the extension cord into the outlet. That's what I'm using and it works great. Little tricky to wire it but I don't...